MYA. GAPER. 106 



Fabricius, in his Fauna Groenlandica, describes the Mya 

 aictica as having two somewhat spinous ridges, which are 

 mostly obsolete, and with the hinge obscurely toothed, a 

 character sufficiently answering to our shell. 



This species, the Mytilus rugosus, and many specimens 

 of the Solen minutus where the spines are obliterated, so 

 much resemble each other, that it is frequently very diffi- 

 cult to distinguish them without a close examination of the 

 hinge. It may however be remarked, that the Mya arctica 

 and the Solen minutus both slope abruptly immediately 

 from the hinge, and are each furnished with a depression 

 on the slope under the hinge ; but that the oblique dorsal 

 ridge of the Mya arctica extends to the front angle of the 

 opposite side, whilst in the Solen minutus this ridge usu- 

 ally reaches about half way down the margin of the oppo- 

 site side, dividing as it were that side into two compart- 

 ments, and giving it an angular appearance, as is well re- 

 presented in Montagu's figure of his Mytilus prsecisus. The 

 Mytilus rugosus differs from both, in not having the hinge 

 close to the end, and in having that side rounded, v. v. 



B. The teeth locking into the opposite valve. 18 to 24. 



! 8. Mya striata. Striated Gaper. 



Linn. Trans, xi. pi. 13. f. 1 A. 



Shell oblong, with the back margin running nearly 

 straight, very thin, semitransparent, finely striate longitu- 

 dinally ; the anterior end truncate, with the valves reflecting 

 and forming a gape when the shell is closed ; the posterior 

 end rounded : beaks small, placed nearer the rounded end ; 

 inside white, with a slight metallic lustre : hinge with a 

 single broad erect tooth in one valve, locking into a cor- 

 respondent cavity in the other : length half an inch ; breadth 

 an inch. 



Found by Mr. Lyons, in Tenby bay : rare. 



19. Mya Batava. Dutch Gaper. 



Lister, pi. 146. f. \Wood y pi. 19. f. 1, 2. 

 Mya Pictorum. Donovan, 61.174. 



Shell pblong-oval, rounded at both ends, olive green in- 

 clining to brown, darker at the longer end, transversely 



striatej 



